syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P17560/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=143121, q=496729 ncpus=2)
task:syz-executor    state:R  running task     stack:20776 pid:17560 ppid:17534  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:check_region_inline mm/kasan/generic.c:169 [inline]
RIP: 0010:kasan_check_range+0x16/0x290 mm/kasan/generic.c:187
Code: ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc 66 0f 1f 00 b0 01 48 85 f6 0f 84 b8 01 00 00 55 41 57 41 56 41 55 <41> 54 53 4c 8d 04 37 49 39 f8 0f 82 5a 02 00 00 49 89 f9 49 c1 e9
RSP: 0018:ffffc9000c887b40 EFLAGS: 00000202
RAX: ffffffff81e7b101 RBX: 0000000000000005 RCX: ffffffff81e7b1aa
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff888018e19028
RBP: dffffc0000000000 R08: ffff888018e18fe7 R09: 1ffff110031c31fc
R10: dffffc0000000000 R11: ffffed10031c31fd R12: ffff888018e19028
R13: 1ffffffff2de2924 R14: ffff888018e18fe8 R15: 0000000000000003
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
 __page_table_check_zero+0x1ba/0x4b0 mm/page_table_check.c:156
 page_table_check_free include/linux/page_table_check.h:41 [inline]
 free_pages_prepare mm/page_alloc.c:1155 [inline]
 free_unref_page_prepare+0x7e1/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2122 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
 put_cpu_partial+0x17c/0x250 mm/slub.c:2738
 __slab_free+0x31d/0x410 mm/slub.c:3686
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
 getname_flags+0xbb/0x500 fs/namei.c:140
 getname fs/namei.c:219 [inline]
 __do_sys_unlink fs/namei.c:4439 [inline]
 __se_sys_unlink fs/namei.c:4437 [inline]
 __x64_sys_unlink+0x3c/0x50 fs/namei.c:4437
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb0edf8df57
RSP: 002b:00007ffeb1bd3188 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb0edf8df57
RDX: 00007ffeb1bd31b0 RSI: 00007ffeb1bd3240 RDI: 00007ffeb1bd3240
RBP: 00007ffeb1bd3240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffeb1bd42d0
R13: 00007fb0ee010b55 R14: 0000000000117643 R15: 00007ffeb1bd4310
 </TASK>
rcu: rcu_preempt kthread starved for 8448 jiffies! g143121 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27432 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lockdep_init_map_type+0x253/0x880 kernel/locking/lockdep.c:4898
Code: 0b 00 48 ba 00 00 00 00 00 fc ff df 84 c0 75 1a 4c 89 ff e8 3f 06 00 00 48 ba 00 00 00 00 00 fc ff df 84 c0 0f 84 7d 01 00 00 <48> 89 d8 48 c1 e8 03 80 3c 10 00 74 12 48 89 df e8 08 f8 75 00 48
RSP: 0018:ffffc90000167aa0 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffc90000167bc8 RCX: ffffffff96eaa401
RDX: dffffc0000000000 RSI: 0000000000000000 RDI: ffffc90000167be9
RBP: ffffc90000167b68 R08: ffffc90000167bdf R09: 0000000000000000
R10: ffffc90000167bd0 R11: fffff5200002cf7c R12: 0000000000000000
R13: 0000000000000000 R14: ffffc90000167bea R15: ffffffff96eed360
 lockdep_init_map_waits include/linux/lockdep.h:192 [inline]
 lockdep_init_map_wait include/linux/lockdep.h:199 [inline]
 lockdep_init_map include/linux/lockdep.h:205 [inline]
 do_init_timer kernel/time/timer.c:850 [inline]
 init_timer_on_stack_key kernel/time/timer.c:806 [inline]
 schedule_timeout+0x147/0x280 kernel/time/timer.c:2165
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.100-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x17/0x60 kernel/kcov.c:216
Code: 48 8b 3d 5c ea c4 0c 48 89 de 5b e9 63 75 56 00 cc cc cc f3 0f 1e fa 48 8b 04 24 65 48 8b 0d 70 24 7e 7e 65 8b 15 71 24 7e 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 1c 16 00 00
RSP: 0018:ffffc900001efd00 EFLAGS: 00000202
RAX: ffffffff813210a2 RBX: ffffc900001efdc0 RCX: ffff88801be5bc00
RDX: 0000000080000101 RSI: 0000000080000101 RDI: 0000000000000000
RBP: ffffc900001efd90 R08: ffff88801be5bc00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000100 R12: ffffffff8a6d3a8c
R13: 00000000000000f0 R14: ffffffff81747100 R15: ffffc900001efd08
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000065030 CR3: 000000002e53b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 000000000000508c
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 arch_stack_walk+0x152/0x190 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 kmem_cache_alloc_node+0x150/0x330 mm/slub.c:3530
 __alloc_skb+0x108/0x2c0 net/core/skbuff.c:640
 alloc_skb include/linux/skbuff.h:1284 [inline]
 synproxy_send_client_synack+0x16d/0xdd0 net/netfilter/nf_synproxy_core.c:460
 nft_synproxy_eval_v4+0x36f/0x560 net/netfilter/nft_synproxy.c:59
 nft_synproxy_do_eval+0x342/0x570 net/netfilter/nft_synproxy.c:141
 expr_call_ops_eval net/netfilter/nf_tables_core.c:240 [inline]
 nft_do_chain+0x3f9/0x1580 net/netfilter/nf_tables_core.c:288
 nft_do_chain_inet+0x25b/0x330 net/netfilter/nft_chain_filter.c:161
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:259 [inline]
 NF_HOOK+0x204/0x390 include/linux/netfilter.h:302
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
 __netif_receive_skb_one_core net/core/dev.c:5596 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5710
 process_backlog+0x380/0x6e0 net/core/dev.c:6038
 __napi_poll+0xc0/0x460 net/core/dev.c:6600
 napi_poll net/core/dev.c:6667 [inline]
 net_rx_action+0x5ea/0xbf0 net/core/dev.c:6803
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d e3 16 3b 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c6
RAX: 36611ed36126f200 RBX: ffffffff81619a5b RCX: 36611ed36126f200
RDX: 0000000000000001 RSI: ffffffff8aaaba40 RDI: ffffffff8afc6700
RBP: ffffc90000187f20 R08: ffff8880b8f36d4b R09: 1ffff110171e6da9
R10: dffffc0000000000 R11: ffffed10171e6daa R12: ffffffff8e4a7da8
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff110037cb780
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>